1) Field of the Invention
The present invention relates to a disk storage that can perform an efficient seek operation.
2) Description of the Related Art
Disk storage is commonly used as a storage medium. In this disk storage, a disk is allocated with areas for data storage and, when reading the data, the disk is rotated and a reading head is made to access a specific area of the rotating disk.
FIG. 9 shows a schematic diagram of conventional disk storage 102. The disk storage 102 comprises an interface 103, a command controller 104, a storage section 105, a head position controller 106, a head operation controller 108, an actuator 107, and a head 109. The reference numeral 110 indicates the disk.
The interface 103 is connected to a host 101, which is an external device. The interface 103 transmits to the command controller 104 a request received from the host 101. The command controller transmits, based on the request received via the interface 103, a command to the head position controller 106 and the head operation controller 108. The head position controller 106 and the head operation controller 108 carry out the reading or writing of data from or to the disk 110. For instance, when the command controller 104 receives a read request from the host 101, it issues, based on the received read request, a seek command that specifies the position, from where the data is to be read, on the disk and a read command that specifies the reading. When the command controller 104 receives a write request from the host 101, it issues, based on the received write request, a seek command that specifies the position, where the data is to be written, on the disk and a write command that specifies the writing.
The command controller 104 transmits the seek command to the head position controller 106. The read command and the write command issued by the command controller 104 are transmitted to the head operation controller 108. The head position controller 106 controls the actuator 107 according to the received seek command, and determines the positions of the disk 110 and the head 109. A seek operation is the moving of the head 109 to a specific area on the disk 110 by controlling the actuator 107. The head operation controller 108, based on the received read command and write command, carries out reading from and writing to the disk 110.
The seek operation of the disk storage 102 is described with reference to FIG. 10. The command controller 104 issues a seek command A based on the request received from the host 101. The command controller 104 then transmits the issued seek command A to the head position controller 106 (operation 121).
The head position controller 106 receives the seek command from the command controller 104 (operation 131) and executes the seek operation (operation 132) by activating the actuator 107 based on the seek command A.
In case the seek command A issued by the command controller 104 is to be abandoned and a different location is to be sought instead, the command controller 104 cannot issue another seek command to the head position controller 106 since the head position controller 106 is already busy executing the seek command A. Consequently, the command controller 104 stands by (operation 122) till the head position controller 106 has finished the seek operation. Once the information that the seek operation has ended is received from the head position controller 106, the command controller 104 issues a seek command B and transmits it to the head position controller 106 (operation 123). After the head position controller 106 receives the seek command B (operation 133), it activates the actuator 107 and executes the seek operation (operation 134).
Thus, in the conventional disk storage 102, the reading from and writing to the disk are carried out when the head 109 accesses the required location of the disk 110 in the seek operation.
However, in the conventional disk storage, when the head position controller 106 is carrying out a seek operation, the next seek command from the command controller 104 cannot be executed until the first seek operation ends. Since the command controller 104 performs many other tasks such as, communication with the host 101, cache control, execution of read command, write command, and others, the operating speed of the storage disk is considerably slowed by having to stand by for the seek operation.
There has been an increasing demand for high-capacity, high-speed disk storage in recent years. Hence, efficient seek command processing has become a crucial factor for meeting the demand. The conventional disk storage thus fails in this respect.